Method of transporting and applying a liquid developer

ABSTRACT

Method and apparatus for transporting and applying a liquid developer to a test piece having dyed indications therein indicative of the presence of flaws, involving directing a stream of a readily volatilizable solvent for a liquid developer from a pressurized source into a container containing the liquid developer to thereby displace some of the liquid developer at a controlled flow rate from the container, injecting the displaced stream into the mixing chamber of a spray nozzle, and propelling the liquid developer and the readily volatilizable solvent through the spray nozzle by the use of an additional stream of the readily volatilizable solvent. While the method and apparatus of the present invention have applicability to any dyed penetrant inspection process in which the developer is applied by spraying to the surface of a test piece containing a dye soluble in the developer, it finds particular utility in the type of procedure described and claimed in the application of Van Kirk and Borrows, Ser. No. 845,012 filed July 25, 1969, now U.S. Pat. No. 3,609,532 issued Sept. 28, 1971, and assigned to the same assignee as the present application.

United States Patent Conner 1 Oct. 28, 1975 METHOD OF TRANSPORTING ANDAPPLYING A LIQUID DEVELOPER [75] Inventor: Kenneth F. Conner, Lombard,Ill.

[73] Assignee: Magnaflux Corporation, Chicago,

[22] Filed: Dec. 2, 1971 [21] Appl. No.: 204,004

[52] US. Cl. 427/8; 427/127; 427/128; 427/130; 427/145; 427/157;427/197; 427/212; 427/336; 427/421 [51] Int. Cl. v. B05C 5/00 [58] Fieldof Search 117/235,104,105.1, 117/105.3105.5; 118/302; 239/373,'143;252/6252; 427/8, 127, 128, 130, 145, 427/157,197, 212, 336, 421

[56] References Cited UNITED STATES PATENTS 2,842,465 7/1958 Harrison239/373 X 2,942,787 6/1960 Bok et a1. 239/373 3,026,045 3/1962 Reading239/143 3,140,050 7/1964 Elmore 239/143 3,609,532 9/1971 Van Kirk252/6252 Primary ExaminerBernard D. Pianalto Attorney, Agent, orFirml-lill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson [57]ABSTRACT Method and apparatus for transporting and applying a liquiddeveloper to a test piece having dyed indications therein indicative ofthe presence of flaws, involving directing a stream of a readilyvolatilizable solvent for a liquid developer from a pressurized sourceinto a container containing the liquid developer to thereby displacesome of the liquid developer at a controlled flow rate from thecontainer, injecting the displaced stream into the mixing chamber of aspray nozzle, and propelling the liquid developer and the readilyvolatilizable solvent through the spray nozzle by the use of anadditional stream of the readily volatilizable solvent.

6 Claims, 1 Drawing Figure METHOD OF TRANSPORTING AND APPLYING A LIQUIDDEVELOPER BACKGROUND OF THE INVENTION Field of the Invention The dyedpenetrant inspection process employing either a fluorescent or visibledye penetrant has been commercially practiced for the last severaldecades. Basically, this inspection procedure involves applying an oilypenetrant containing either a fluorescent dye or a visible dye over thesurface of the test piece and permitting the penetrant to wet the metal,and become lodged in any surface discontinuities which may exist. Excesspenetrant is then removed from the surface by emulsification, scrubbingor washing to leave only the entrapped dye penetrant in the flaws. Thesurface tension characteristics of the penetrant are such that it tendsto exude from the flaws, seeping out to the surface where it can beobserved and thereby indicate the location and the extent of any surfaceflaws.

The visibility of the indication is enhanced'by the application to thesurface of the part of a developer 'containing light-colored pigmentparticles which render the dyed penetrant exudate or residuecontrastingly visible. The pigment particles act in the manner of ablotter to extract residual penetrant by capillary action and also toprovide a background against which the dyed penetrant residue isrendered more clearly visible. The developer may consist solely offinely divided particles, but in many instances, the developer isapplied as a suspension of finely divided pigment particles in anonaqueous liquid which contains or is itself a volatile solvent for thedye. The solvent thereby enhances the development action by dissolvingthe dyed penetrant and bringing it to the surface where it spreads intothe finely divided layer of pigment particles.

Another form of non-destructive testing involving dyed testing materialsis that which concerns itself with the use of magnetic particles coloredwith a dye which becomes visible upon activation by certain solvents,and magnetic particles coated with a fluorescent dye. Examples ofmethods and compositions employing such magnetic particles will be foundin the de Forest US. Pat. No. 2,365,253; Kazenas US. Pat. No. 2,936,287;Borrows US. Pat. No. 3,404,093; Borucki et al. US. Pat. No. 3,485,758;and Lorenzi US. Pat. No. 3,480,855.

A novel method and apparatus for jointly employing both the magneticparticles colored with a solvent activated dye and magnetic particlescolored with a fluorescent dye and described in the aforementioned US.Pat. No. 3,609,532. That patent describes a method of detectinginhomogeneities, defects, flaws or other discontinuities in work piecesand, in general, solid objects that are magnetizable such as ferrousmetal objects. A'flowable mixture of fluorescent dye-colored magneticparticles and visible dye-colored magnetic particles is "applied to thework piece by sprinkling, pouring or spraying. The particles can beapplied in dry form or they can be applied in a liquid suspendingmedium. Preferably, relative movement is effected between the flowablemixture during its application to the work piece and the surface towhich the mixture of particles is applied so that an accumulation. ofmagnetic particles occurs only where there is a magnetic leakage fieldcaused by a surface discontinuity. The adherent 2 magnetic particles arethen subjected to the action of a liquid solvent which is a solvent forthe visible dye of the visible dye-colored particles, thereby causing adissolution of the visible dye in the solvent or a bleeding of the dye.

One of the advantages of the aforementioned process is that it gives anearly and easily observed indication of surface discontinuities in thework piece due to the accumulation of fluorescent magnetic particles atany surface discontinuities, while the subsequent color indicationprovides by the bleeding of the visible dye affords a highly contrastingcolor indication under ordinary, or white light. By incorporating alight-colored pigment in the solvent for the visible dye, a desiredcolor contrast is obtained.

The aforementioned type of inspection process has proven to be verysatisfactory in the location and identification of inhomogeneities.There has been some difficulty encountered, however, in the matter ofapplying the liquid developer containing suspended pigment SUMMARY OFTHE INVENTION The present invention provides a system for transportingand applying a liquid developer to a test piece in which dyedindications are present which involves directing a first gaseous streamof a readily volatilizable solvent for the liquid developer from apressurized source into a container containing the liquid developer tothereby displace some of the liquid developer at a controlled flow ratefrom the container. The displaced stream is directed to the fluid nozzleof a spray means and there combined with a stream of the readilyvolatilizable solvent, which also propels the mixed streams and servesto eject the combined developer-solvent mixture through the spray nozzleas a finely divided atomized spray. The continuous solvation of theliquid developer by the presence of the readily volatilizable solventkeeps the material from drying out and also serves to prevent pluggingor the orifice nozzle from continued use.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantagesof the invention will be readily apparent from the following descriptionof a preferred embodiment thereof, taken in conjunction with theaccompanying drawing, although variations and modifications may beeffected without departing from the spirit and scope of the novelconcepts of the disclosure, and in which:

The single FIGURE in the drawing is a somewhat schematic representationof a spraying system which can be used for delivering and atomizing aliquid developer composition in accordance with the improvements of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawing, referencenumeral 10 has been applied generally to a pressure vessel which holds amaterial which is a solvent for the liquid constituent of the developer.The fluorocarb'ons are particularly preferred, but other low boilingliquids or pressurized gases such as low boiling hydrocarbons and thelike can be used as long as they produce the desired effect of acting asa solvent for the liquid being sprayed and provide the pressure toconvey the liquid through the'system and secure the desired spraypattern.

Any of the commercially available fluorocarbon's can be used eitheralone or in combination to provide the requisite vapor pressurecharacteristics, as is well known to those skilled in this art. Thefollowing represents a partial list of such fluorocarbons:

Commercial name Chemical name 'Freon-l l trichloromonofluoromethaneFreon l 2 dichlorodifluoromethane Frconl 3 monochlorotrichloromethancFreon-13B] monobromotrifluoromethanc Freonl4 tetrafluoromethane QFreon-22 'monochlorodifluoromethane Freon-H3 trichlorotrifluoroethancFreon-l l4 dichlorotetrafluoroethanc of light colored pigment particlesof very finely divided particle form in-a non-aqueous, readilyvolatilizable ve- -hicle. Such non-aqueous vehicles can be alcohols orvolatile liquid materials such as trichlorethane, methylene chloride, ortrichloroethylene. The solvent may also be a liquid ketone such asacetone or methyl isobutyl. ketone, or the like. The developer may alsoinclude resinous materials which serve to increase the viscosity of thedeveloper while inhibiting spreading of the visible dye indication tothe proximity of the surface discontinuity. Such resinous materials maybe polyvinyl chloride dissolved in a relatively volatile hydrocarbonsolvent or a lacquer-type solvent developer such as nitrocellulose andamyl or butyl acetate.

The finely divided particles contained in the developer may be materialsuch as talc or chalk, to cite two common examples. A uniform dispersionof the finely divided particles in the non-aqueous vehicle is providedby employing an agitator 16 which is driven by an air motor 17 having acompressed air inlet 18 and an air exhaust 19.

Upon introduction'of the pressurized gas from the pressure vessel 10into the tank 15,'the additional pressure serves to force liquid in thetank through a discharge tube 20 having its inlet end near the bottom ofthe tank 15. This discharged liquid is passed into a conduit 21 underthe control of a manual shut-off valve 22 and then into a metering valve23 by means of which 4 ber 26. The gas, being a solvent for the liquidin the developer solution keeps the solution solvated and at a viscositysuitable for spraying as well as atomizing the developer as it passesthrough the spray nozzle.

On-off control for the spray nozzle is provided by a branch conduit 31which is connected behind the manual valve 11. A solenoid operated valve32 disposed in a branch line 33 is actuated by an electrical signal toinject the propellant gas through a pressure regulator and gaugeassembly 34 into an inlet 35.

Disposed within the spray nozzle assembly 25 is a needle valve 36 havinga headed portion 37 slidably received within a cylinder 38. A spring 39normally biases the needle valve 36 in a position in which it closes offthe spray nozzle 27. The inlet 35 introduces the pressurized gas into aspace between the headed portion 37 and a rigid plate 40 through whichthe needle valve 36 may slide, but which prevents gas flow into themixing chamber 26. When the gas pressure is sufficiently high, theneedle valve 36 is unseated, and the mixture of developer and solvent issprayed out into the atmosphere.

Any one of a wide variety of developer compositions can be used and thefollowing areoffered strictly for purposes of example:

Trichloroethylene l l0 gals.

TiO CaCO silica l 10 lbs.

lsooctyl phcnoxy polyethoxy ethanol (9-l0) oxyethylenc groups) 3 galsv 6lbs.

Zinc stearatc 50/50 mixture of ethanol and ethyl acetate I I0 gals.Mixture of TiO and SiO I ll) lbs.

Nonyl phenol polyethylene glycol ether 3 gals.

The solvent contained in the developers when applied to a visible dyecontained on ferromagnetic particles results in the production of avisible dye solution which spreads out over the magnetic pigmentparticles in the manner of a paint to give a brightly coloredenlargement of the indication against a strongly contrasting backgroundcreated by the white or light colored pigment contained in the liquiddeveloper. The system lends itself to automatic operation through theuse of an automatic black light scanner so that developer is sprayed ononly at the location required or indicated by the presence of thefluorescent indications.

I claim as my invention:

1. The method of transporting and applying a liquid developer to a testpiece having dyed indications therein indicative of the presence offlaws which compn'ses directing a first gaseous stream of areadilyvolatilizable solvent for a liquid developer from a pressurized sourceinto a container containing said liquid developer to thereby displacesome of said liquid developer at a controlled flow rate from saidcontainer, directing the displaced liquid developer to a spray means,

directing a second gaseous stream of said solvent at a controlled ratefrom said pressurized source into said spray means,and discharging fromsaid spray means a spray of a resulting developersolvent liquid at thesur- 4 face of said test piece.

4. The method of claim 3 in which said particles are pigment particleswhich provide a contrasting background for said dye.

5. The method of claim 3 in which said vehicle is an alcohol.

6. The method of claim 1 which includes the step of directing a thirdpressurized gaseous stream of said solvent into said spray means toactuate said spray means.

1. THE METHOD OF TRANSPORTING AND APPLYING A LIQUID DEVELOPER TO A TESTPIECE HAVING DYDED INDICATION THEREIN INDICATIVE OF THE PREANCE OF FLAWSWHICH COMPRISES DIRECTING A FIRST GASEOUS STREAM OF A READILYVOLATILIZABLE SOLVENT FOR A LIQUID DEVELOPER FROM A PRESSURIZED SOURCEINTO A CONTAINER CONTAINING SAID LIQUID DEVELOPER TO THEREBY DISPLAC SOMOF SAID LIQUID DEVELOPERR AT CONTROLLED FLOW RATE FROM SAID CONTAINER,DIRECTING THE DISPLACED LIQUID DVELPPER TO A SPRAY MEANS, DIRECTING ASECOND GASEOUS STREAM OF SAID SOLVENT AT A CONTROLLED RATE FROM SAIDPRESSURIZED SOURCE INTO SAID SPRAY MEANS, AND DISCHARGING FROM SAIDSPRAY MANS A SPRAY OF A RESULTING DEVELOPERSOLVENT LIQUID AT THE SURFACEOF SAID TEST PIECE.
 2. The method of claim 1 in which said dyedindications consist of a mixture of finely divided magnetic particlessome of which have a fluorescent pigment adhering thereto and others ofsaid particles have a potentially visible dye adhering thereto whichbleeds in contact with said liquid developer.
 3. The method of claim 1in which said liquid developer consists of a suspension of finelydivided particles in a non-aqueous vehicle.
 4. The method of claim 3 inwhich said particles are pigment particles which provide a contrastingbackground for said dye.
 5. The method of claim 3 in which said vehicleis an alcohol.
 6. The method of claim 1 which includes the step ofdirecting a third pressurized gaseous stream of said solvent into saidspray means to actuate said spray means.